Field of the Invention
The present invention relates to a luminous light emitting device, a light source unit including this luminous light emitting device, and an image projection system including this light source unit.
Description of the Related Art
In an image projection system in which laser light emitting devices are used as a light source to emit laser light and luminous light which is produced to be emitted by exciting a luminescent material using the laser light as excitation light so as to form bright image forming light source light by combining the laser light and the luminous light together to thereby emit highly bright image light, in the event that optical members which are incorporated in a light source unit get dirty as a result of the passage of time, there may occur a situation in which the brightness of an image is deteriorated although it is slight. As this occurs, various problems are caused which include deterioration not only in brightness but also in tonality and definition of a projected image, an increase in calorific power in an optical system and the like.
To deal with those problems, the applicant of this patent application proposed a light source unit and a projector in Japanese Unexamined Patent Publication No. 2015-222300. In this light source unit, a light source of lights of the three primary colors is provided by combining together a light source which includes a plurality of laser light emitting devices and a rotatable luminescent plate of a luminescent material in a combined fashion and a light source made up of a red light emitting diode. Then, the light source of lights of the three primary colors, a display device such as a digital micromirror device (DMD) which forms image light and a projection lens which makes up a projection optical system are accommodated in an interior of an optical unit, and the light source devices and the optical devices are sealed in the interior of the optical unit to protect them from dirt. In addition, heat from the various heat sources can be dissipated effectively.
Then, the proposed projector includes various heat sources such as a control circuit which is a projector control unit which includes a CPU configured as an arithmetic unit and a power supply circuit which supplies electric power to the light source unit. In addition to these heat sources, the projector includes the light emitting sources such as the laser light emitting devices and the light emitting diode and the rotatable luminescent plate onto which the laser lights are collected. These light emitting sources and the luminescent plate also have great calorific power. Thus, various heat dissipating measures are taken in this projector.
Japanese Unexamined Patent Publication No. 2002-090886 relates to a color wheel which resembles a luminescent wheel of a luminescent material which is a rotatable luminescent plate of a luminescent material and proposes a technique to enhance the heat dissipating effect of the color wheel by accommodating the color wheel in a tightly closed case and providing heat dissipating fins on an external surface of the case.
With the light source unit which uses the semiconductor light emitting devices such as the laser light emitting devices and the luminous light emitting plate made up of the luminescent material, it is easy to form bright lights of the three primary colors to thereby enable the projection of a bright image.
However, the light sources with high luminance brightness have great calorific power, thereby making it difficult for those light sources to make up a light source unit which is small in size and which exhibits high cooling and heat dissipating effects.
In particular, the heat dissipation of a member like the luminescent wheel which is driven to rotate is different from the heat dissipation of the fixed portions such as the projector control circuit, the power supply circuit and the light emitting devices, and it is difficult to dissipate heat from the rotary member effectively. In the event that the temperature of the luminescent wheel is raised, there is the possibility that problems are caused which include a reduction in luminous efficiency and a quick deterioration of the luminescent material to shorten the life thereof.